1. Field of the Invention
The present invention relates to a direction restricting device for the inner and outer tubes of a bicycle seat post and, more specifically, to a structure that may eliminate the rotary interspace between the inner tube and the outer tube of a bicycle seat post to prevent deflection and wobble when said inner and outer tubes rotate relative to each other.
2. Description of the Prior Art
The seat post is used for supporting the seat, and, normally, the seat post of a bicycle includes at least an outer tube and an inner tube joined to each other to adjust the seat height. In order to prevent the outer tube and the inner tube from rotating, generally, a direction restricting device is arranged between the inner and outer tubes to limit the inner tube to axial movements, such as the direction restricting arrangement of the bicycle suspension system disclosed in U.S. Pat. No. 6,145,862. According to FIG. 3B shown in U.S. Pat. No. 6,145,862, a plurality of sets of opposing flats is arranged between the outer tube and the inner tube, and needle bearings are disposed between the opposing flats to allow the inner tube to freely slide within the outer tube. However, the height of the needle bearings may become varied after operating for a long time. That is, the needle bearings may not stay in the same horizontal position relative to the height, because the contacted friction planes and the friction resistances between the outer tube and the inner tube are different. Therefore, the measurement or height that the inner tube moves axially within the outer tube will be affected. In order to ameliorate the aforementioned drawback, the seat post needs to be taken apart to adjust the needle bearings to stay in the same horizontal position relative to the height. In addition, an interspace occurs between the axial walls of the aforesaid opposing flats between the outer tube and the inner tube, and said interspace may cause deflection and wobbling of the tubes when the inner and outer tubes rotate.
It is against this background and the problems associated therewith that the present invention has been developed.